<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<div style="width: 500px;border: 1px solid red">
    <div style="width: 20%; background-color: gold; float: left" >a</div>
    <div style="width: 20%; background-color: firebrick; float: left" >b</div>
    <!--<div style="clear: both"></div>-->
</div>
</body>
</html>